GB1013509A - Process for the purification of pyrolysis gases - Google Patents

Abstract

<FORM:1013509/C4-C5/1> A process for removing carbon dust, tar and hydrocarbons containing 8 or more carbon atoms per molecule from pyrolysis gases comprises simultaneously scrubbing and partially cooling by quenching the gases with a relatively hot hydrocarbon oil (e.g. at 100 DEG to 150 DEG C.) in a first zone 5, and completing the cooling by scrubbing with water under highly turbulent flow conditions (to prevent mist formation) in a second zone 17. Condensed oil (at 24) and dust (at 23) are separated, at 21, from the water (at 22), and a major portion of the condensed oil is recycled (via 24 . . . 26) to the zone 5, and a minor portion of the oil is discharged (at 27) for recovery of cyclic hydrocarbons, e.g. xylene, styrene, indene, and naphthalene, contained therein. The scrubbing oil may be a petroleum light oil (initial b.p. above 150 DEG C.). Turbulent flow in the zone 17 is achieved by using a perforated plate tower with impact plates over the perforations, whereby gas velocities through the perforations above 5 m./sec. are obtained. Preferably, as shown, the oil is sprayed at 3 into the gases, which, with vaporized and unvaporized oil, enter a distillation column 5 where oil condenses and from which dust-containing oil is discharged at 6 for separation at 7, oil being recycled, after being suitably made up, at 10, via lines 13, 15. The unsaturated component of the heavy hydrocarbons is polymerized to tar and eliminated via line 6, the gases leaving the column via line 16 containing vaporized oil and mainly cyclic hydrocarbons. In a modification, Fig. 3 (not shown), a heat-exchanger is inserted in the line 16 and condensate (water and oil) removed from the exchanger, separated, a major part of the oil recycled to the top of the column 5, and a minor part discharged for recovery of cyclics. Further, fresh oil is delivered to the top of the scrubber 17 to remove cyclic hydrocarbons, the oil being separated from the water at 21, as before, and part at least delivered via line 26 directly to the line 13. Two examples are described.